Maemo5 uses Evolution-Data-Server as its backend for contacts, hence the proper way would be to implement this in e-d-s first.
That's why you've filed https://bugzilla.gnome.org/show_bug.cgi?id=640203 .

Basically Maemo5 will not receive new features as it is considered stable by Nokia and future development happens on meego.com.
There are also community efforts to provide Maemo5 updates ("Community SSU").